V1/man/man4/ppt.4

        11/3/71                                                 /DEV/PPT (IV)


NAME              ppt -- punched paper tape

SYNO?S IS

DESCRIPTION       ppt refers to the paper tape reader or punch, depending on
                  whether it is read or written.

                  When is opened for writing, a 100--character leader is
                  punched. Thereafter each byte written is punched on the
                  tape. No editing of the characters is performed. When the
                  file is closed, a 100--character trailer is punched.

                  When ppt is opened for reading, the process waits until
                  tape is placed in the reader and the reader is on--line.
                  Then requests to read cause the characters read to be
                  passed back to the program, again without any editing.
                  This means that several null characters will usually
                  appear at the beginning of the file; they correspond to
                  the tape leader. Likewise several nulls are likely to
                  appear at the end. End--of--file is generated when the tape
                  runs out.

                  Seek calls for this file are meaningless and are
                  effectively ignored (however, the read/write pointers are
                  maintained and an arbitrary sequence of reads or writes
                  intermixed with seeks will give apparently correct results
                  when checked with tell).

FILES

SEE ALSO          lbppt, dbppt, bppt format

DIAGNOSTICS

BUGS              Previously, there were separate special files for ASCII
                  tape (which caused null characters to be suppressed) and
                  binary tape (which used a blocked format with checksums).
                  These notions were conceptually quite attractive, but they
                  were discarded to save space in the system.

OWNER             ken, dmr